In general, a trailing arm attachment part which attaches a trailing arm of a rear wheel suspension to a vehicle body is required to have high rigidity from the viewpoint of steering stability, and the like. Means conventionally used to achieve high rigidity in a trailing arm attachment part includes: a configuration using a reinforcing member in the attachment part, a configuration which increases the plate thickness of the attachment part, or a configuration which forms the attachment part from a high-strength member, and so on. However, each of these approaches inhibits weight reduction, as well as leading to increased costs, and consequently there has been scope for improvement from the viewpoint of weight reduction and cost.
More specifically, the trailing arm attachment part is subject to the following requirements: (a) the part must have high rigidity from the viewpoint of steering stability, and the like; (b) the part must be positioned higher than the wheel center, from the viewpoint of steering stability, and the like; and (c) the part must be horizontal from the viewpoint of the ease of assembly.
Effective means for achieving (b) and (c) above is to provide a horizontal portion in the kick-up part of the rear frame. However, in this case, an inclined part having a relatively steep angle of incline is formed in the rear frame described above. Furthermore, in the event of a front collision, the load of the collision is liable to be concentrated in the inclined part, and therefore it is necessary to improve rigidity in the vicinity of the inclined part and to transmit the collision load in a smooth fashion.
Patent Document 1 discloses providing a kick-up part having a rear rising incline which links a side sill rear part and a rear frame front part in a low-front and high-rear fashion, and providing an attachment part for attaching the trailing arm of a rear wheel suspension on the kick-up part. However, in the prior art structure disclosed in Patent Document 1, since an opening section passing through the front linking end of the trailing arm is formed with a large opening in the kick-up part, then the rigidity becomes lower although the weight of the components increases, and there has been scope for weight reduction.
Patent Document 1: Japanese Patent Application Publication No. 2007-290665